ERBB4 and mucinous adenocarcinoma of the appendix: In appendiceal cancers, mutations in the EGFR/ERBB1 gene are found in well-differentiated neuroendocrine tumors of the appendix [37]; mutations in HER2/ERBB2 gene are associated with the adenocarcinomas of the appendiceal goblet cells, well-differentiated neuroendocrine tumors of the appendix, and mucinous adenocarcinomas of the appendix; and those in the HER4/ERBB4 gene in well-differentiated neuroendocrine tumors of the appendix [37].